1. Field of the Invention
The present invention relates generally to an image displaying apparatus in which a prescribed pointing character is displayed with a displayed image at a prescribed position, and more particularly to an image displaying apparatus suitable for a presentation apparatus in which a pointer marker such as an arrow is displayed as a pointing character on a displayed image.
2. Description of the Related Art
2.1. Previously Proposed Art
In cases where a presentation is performed in a meeting such as a lecture meeting, a presentation apparatus such as an overhead projector or a video projector is used to display an image on an image screen. In this case, to point out a prescribed position on the displayed image, a pointing stick or a laser pointer is used as one of pointing methods. Also, as another pointing method, a pointing signal indicating a pointer marker is superimposed on a picture signal, and the pointer marker is directly displayed with an image on the image screen.
To directly display a pointer marker on an image screen, there is an idea that an image displaying apparatus useful only for a presentation apparatus is used. However, it is expensive to use an image displaying apparatus applied for only for a presentation apparatus because it takes development costs for the image displaying apparatus. Therefore, in cases where an on-screen displaying circuit generally used for a television unit or a monitor unit is used to directly display a pointer marker on an image screen, a pointer marker can be displayed on an image screen at a low cost.
2.2. Problems to be Solved by the Invention
However, in cases where the on-screen displaying circuit is used, a display performance for displaying a pointer marker (or a pointing character) indicating a prescribed position on a displayed image depends on a display performance of the on-screen displaying circuit. For example, in cases where an on-screen displaying circuit, in which 22 characters can be displayed in the lateral direction and 18 characters can be displayed in the longitudinal direction, is used, a display performance for the pointer marker becomes 22 characters in the lateral direction and 18 characters in the longitudinal direction. In other words, a display position of the pointer marker is limited to one of positions of 22 characters in the lateral direction and is limited to one of positions of 18 characters in the longitudinal direction. Therefore, there is a drawback that the display performance for the pointer marker is not sufficient.
This drawback is described in detail with reference to FIG. 1. FIGS. 1A and 1B respectively show a position input by a user to a touch screen panel and a position pointed on an image screen by a pointer marker which is displayed according to a pointing signal obtained by processing the input position in the on-screen displaying circuit. Here, the touch screen panel is used as a coordinate input unit, and the pointer marker is indicated by an arrow. Also, lateral positions of the touch screen panel are indicated by lateral coordinates X1, X2, X3,--, longitudinal positions of the touch screen panel are indicated by longitudinal coordinates Y1, Y2, Y3,--, lateral positions of the image screen are indicated by the lateral coordinates X1, X2, X3,--, and longitudinal positions of the image screen are indicated by the longitudinal coordinates Y1, Y2, Y3,--. Therefore, each of partitioned input blocks of the touch screen panel is indicated by coordinates (Xi,Yi), and each of partitioned display blocks of the image screen is indicated by coordinates (Xi,Yi).
A character area in which one character is displayed is composed of four partitioned display blocks adjacent to each other in the image screen, and each character area is indicated by a closed dotted line in FIGS. 1A and 1B. Therefore, a display performance of the on-screen displaying circuit corresponds to one character area. That is, an image indicated by a picture signal transmitting through the on-screen displaying circuit can be displayed on every character area. In contrast, because a user can input a position to a touch screen panel for each partitioned input block, a position receiving performance of the touch screen panel corresponds to one partitioned input block indicated by coordinate (X,Y).
Therefore, as shown in FIG. 1A, in cases where the partitioned input block (X1,Y1) of the touch screen panel is input by the user, the partitioned display block (X1,Y1) of the image screen is pointed out by a pointer marker because the partitioned display block (X1,Y1) represents one character area corresponding to the partitioned input block (X1,Y1). Also, in cases where a block input by the user is changed to the partitioned input block (X2,Y1), it is desired that a block pointed out by the pointer marker is changed to the partitioned display block (X2,Y1) of the image screen corresponding to the partitioned input block (X2,Y1). However, as shown in FIG. 1B, because the partitioned display block (X1,Y1) represents the character area corresponding to the partitioned input block (X1,Y1), a block pointed out by the pointer marker is undesirably maintained to the partitioned display block (X1,Y1). In other words, because a display performance of the pointer marker depends on that of the on-screen displaying circuit, the partitioned display block (X2,Y1) of the image screen cannot be pointed out by the pointer marker.
Also, in cases where the user moves his finger while keeping the contact of the finger with the touch screen panel, even though a position input by the user to the touch screen panel is continuously changed, the pointer marker displayed on the image screen is discontinuously moved every two partitioned display blocks (or every character area), the pointer marker cannot be smoothly moved. For example, when the position input by the user to the touch screen panel is changed from the partitioned input block (X1,Y1) to the partitioned input block (X3,Y1) through the partitioned input block (X2,Y1), the pointer marker is directly moved from the partitioned display block (X1,Y1) to the partitioned display block (X3,Y1). Therefore, the user receives an uncomfortable feeling.
To avoid the discontinuous moving of the pointer marker, there is an idea that a display performance of the on-screen display circuit is improved. For example, the on-screen display circuit is improved to display the pointer marker for each partitioned display block or to halve the moving interval of the pointer marker. However, the improvement of the on-screen display circuit requires a high cost, and the purpose of displaying a pointer marker on an image screen at a low cost by using an on-screen displaying circuit generally used for a television receiver or a monitoring unit comes to nothing.